Synaptic signaling between neurons and glia
Synaptic signaling between neurons and glia
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DOI：
10.1002/glia.20060
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发表时间：
2004-08-15
期刊：
影响因子：
6.2
通讯作者：
Bergles, DE
中科院分区：
文献类型：
--
作者：
Lin, SC;Bergles, DE
脊椎动物神经元之间的快速信号主要发生在突触，细胞间连接处，神经递质的量释放通过激活嗜离子受体触发膜电导的快速变化。神经胶质细胞表达许多相同的嗜离子受体，但对神经胶质细胞中的受体如何原位激活知之甚少。由于突触被认为是神经元的唯一来源，人们一直认为这些受体必须在递质从突触间隙扩散后被激活，或者通过非突触机制（如转运体逆转）被激活。最近的两份报告表明，一类普遍存在的表达蛋白聚糖NG2 （NG2细胞）的祖细胞通过直接的神经元-胶质突触参与谷氨酸能和γ -氨基丁酸（GABA）能神经元的快速信号传导。神经元在这些位点大量释放递质会触发NG2细胞中氨基甲基异恶唑丙酸（AMPA）或GABA(A)受体的快速激活。这些电流表现出与直接而非外溢介导的传递一致的特性，电子显微图分析表明，含有突触囊泡簇的神经末梢与NG2细胞突起形成离散连接。虽然AMPA或GABAA受体的激活使NG2细胞去极化，但这些受体更可能作为离子通量的途径，而不是去极化的电流源，因为突触瞬态的振幅很小，NG2细胞的静息膜电位高度负。谷氨酸和GABA在体外影响NG2细胞的形态、生理和发育的能力表明，这种快速的信号形式可能在体内调节这些细胞的行为以适应周围神经元的需要方面发挥重要作用。(C) 2004 Wiley-Liss, Inc。
Rapid signaling between vertebrate neurons occurs primarily at synapses, intercellular junctions where quantal release of neurotransmitter triggers rapid changes in membrane conductance through activation of ionotropic receptors. Glial cells express many of these same ionotropic receptors, yet little is known about how receptors in glial cells become activated in situ. Because synapses were thought to be the sole provenance of neurons, it has been assumed that these receptors must be activated following diffusion of transmitter out of the synaptic cleft, or through nonsynaptic mechanisms such as transporter reversal. Two recent reports show that a ubiquitous class of progenitors that express the proteoglycan NG2 (NG2 cells) engage in rapid signaling with glutamatergic and gamma-aminobutyric acid (GABA)ergic neurons through direct neuron-glia synapses. Quantal release of transmitter from neurons at these sites triggers rapid activation of aminomethylisoxazole propionic acid (AMPA) or GABA(A) receptors in NG2 cells. These currents exhibit properties consistent with direct rather than spillover-mediated transmission, and electron micrographic analyses indicate that nerve terminals containing clusters of synaptic vesicles form discrete junctions with NG2 cell processes. Although activation of AMPA or GABAA receptors depolarize NG2 cells, these receptors are more likely to serve as routes for ion flux rather than as current sources for depolarization, because the amplitudes of the synaptic transients are small and the resting membrane potential of NG2 cells is highly negative. The ability of both glutamate and GABA to influence the morphology, physiology, and development of NG2 cells in vitro suggests that this rapid form of signaling may play important roles in adapting the behavior of these cells to the needs of surrounding neurons in vivo. (C) 2004 Wiley-Liss, Inc.